Melt butter of medium heat in large stock pot. Cook onion until soft (about 3-5 mins)
Add flour and blend to make roux.
Add seafood stock to roux, stirring well. Reduce to low heat and stir until thickened (about 5 mins)
Stir small amount of hot roux into cream to temper.
Add cream and bring to a boil.
Reduce heat to low. Add next 5 ingredients, 1 tsp of salt, and 1/2 of the crab. Simmer 5 mins.
Combine remaining crab meat, salt, and sherry in a small bowl. When you divide the soup into individual bowls, top with a scoop of the crab mixture in the center of the bowl.